This invention relates to tape drives and, in particular, to an apparatus that implements a magnetic tape threading mechanism for threading the magnetic tape from the single reel magnetic tape cartridge into the takeup reel and a separate magnetic tape wrap mechanism for transporting the threaded magnetic tape into position against the data read/write head, wherein the tape drive is implemented in a compact space, such as a 5xc2xc inch by 8 inch form factor.
It is a problem in the field of data processing systems to provide an apparatus to efficiently store data on a data recording medium while working within the constraints imposed by the industry standard data storage media, data storage formats, tape drive architectures, and tape drive form factors. This is especially a problem in the case of adapting single reel leader block based magnetic tape cartridge tape drive mechanisms to a small form factor to conserve space. The magnetic tape threading mechanisms that are typically used in the magnetic tape cartridge tape drives are typically complex and consume a significant amount of space in the tape drive. In particular, a single reel magnetic tape cartridge has a leader block attached to one end of the magnetic tape that is housed therein. A tape threading mechanism threads the leader block end of the magnetic tape from the magnetic tape cartridge to a takeup reel that is permanently mounted in the tape drive over a predefined tape threading path that includes the read/write head as well as a plurality of bearings to guide the magnetic tape. The takeup reel includes a slot for receiving the leader block and is connected to a drive motor for transporting the tape between the takeup reel and the magnetic tape cartridge. In order to follow the complex tape threading path, existing tape drives use a jointed tape threading arm, whose path is determined by a cam track. The cam track has a beginning point for positioning a longitudinal cam member into engagement with the leader block that is exposed through an opening in the magnetic tape cartridge. The tape threading arm is connected at one end to the longitudinal cam member and at the other end to a servo controlled drive motor. The drive motor activates the tape threading arm to transport the longitudinal cam member from the end of the cam track, where it engages the leader block, to a slot in the takeup reel, threading the magnetic tape through the tape threading path as it traverses this path. Due to the complex nature of the tape threading path, a servo mechanism controls the tape threading arm operation to pull the magnetic tape at a constant speed and provide a constant tension on the tape as it is being withdrawn from the magnetic tape cartridge and transported to the takeup reel. The problem with this architecture is that the tape threading mechanism occupies a significant amount of space in the tape drive, is mechanically complex and costly.
In contrast, the helical scan data read/write technology that is based on the video data storage industry, uses a dual reel magnetic tape cassette as the data storage medium. The magnetic tape cassette contains both the source reel and the takeup reel, located juxtaposed to each other and rotatably mounted on associated spindles. When the magnetic tape cassette is loaded in the tape drive, the tape drive magnetic tape loading mechanism withdraws a length of the exposed magnetic tape from the magnetic tape cassette and wraps the magnetic tape around the rotary read/write head. When the magnetic tape is in this position, the drive motors transport the magnetic tape from the source reel to the takeup reel over the read/write head, and data can be read from or written to the magnetic tape. While the tape wrap mechanism in this tape drive is simple and inexpensive, the tape drive occupies a significant amount of space. In particular, the width of the tape drive is greater than the width of a dual reel tape cassette in order to enable the wrapping of the magnetic tape about the associated rotary heads. The use of this amount of horizontal space is costly, especially in the environment of automated cartridge library systems that robotically store and retrieve magnetic tape cartridges. The minimization of the space required for the tape drive in an automated cartridge library system increases the storage capacity of the system, thereby reducing the per magnetic tape cartridge storage cost.
The integration of these two above-noted tape drive technologies into a rotary head based single reel magnetic tape cartridge tape drive is illustrated in U.S. Pat. No. 5,128,815 wherein an interface is used to present the magnetic tape cartridge to the rotary head mechanism in a manner that emulates the magnetic tape cassette media. This is accomplished by providing a takeup reel that is permanently mounted in the tape drive and positioned with respect to the magnetic tape cartridge in a relationship that substantially mimics the format of the magnetic tape cassette. A short tape threading arm is used to retrieve the leader block end of the magnetic tape from the magnetic tape cartridge and thread the magnetic tape over a short tape threading path to the takeup reel. Once the leader block is inserted into the takeup reel, a rotary head tape wrap mechanism transports the exposed length of magnetic tape, that extends from the magnetic tape cartridge to the takeup reel, to the rotary heads that are located in a position with respect to the magnetic tape cartridge and takeup reel to be compatible with the tape cassette mode of operation. However, while the tape threading and the tape wrap mechanisms in this tape drive are simple and inexpensive, the tape drive occupies a significant amount of space. In particular, the width of the tape drive is greater than the width of a dual reel tape cassette in order to emulate this format for the associated rotary heads in spite of the fact that only a single reel magnetic tape cartridge is processed by this tape drive.
It is therefore desirable in single reel magnetic tape cartridge tape drives to package the mechanisms that comprises the tape drive into the minimum volume and more particularly minimum width and height dimensions. Within this predefined volume, a tape threading mechanism must extract the leader block from the magnetic tape cartridge and load the leader block into a takeup reel while also positioning the magnetic tape around a set of tape guides and the read/write head. In addition, the tape elevator, electronics and other standard tape drive assemblies must be included in the predefined volume. The implementation of these mechanisms is preferably achieved within a 5xc2xc inch by 8 inch form factor. However, this concept can be used with other tape drive form factors to minimize the space required and to provide a longer tape path. This permits the use of a thinner magnetic tape which in turn permits the use of a greater length of magnetic tape on the tape reel, thereby providing greater data storage capacity.
The above described problems are solved and a technical advance achieved by the present compact tape drive for reading and writing data on single reel magnetic tape cartridges that functions to implement the tape drive in a minimum predefined volume. The compact tape drive comprises a tape threading mechanism that extracts the leader block from the magnetic tape cartridge and loads the leader block into a takeup reel that is located juxtaposed to the loaded magnetic tape cartridge. The read/write head is located adjacent to the takeup reel and the loaded magnetic tape cartridge. A separately operable magnetic tape wrap mechanism comprising a plurality of cooperatively operative tape wrap arms is also provided to position the magnetic tape around a set of tape guides and the read/write head. The magnetic tape wrap mechanism functions both to thread the magnetic tape around the takeup reel, spanning the space in front of the read/write head, and then to wrap the magnetic tape around the read/write head. In addition, the tape elevator, electronics and other standard tape drive assemblies are included in the predefined volume, preferably comprising a 5xc2xc inch by 8 inch form factor.